VIX Snapshot

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations declare readOnlyHint=true, and the description does not contradict that. The description adds useful context by noting the return includes level, change, and term-structure state, but it does not disclose additional behavioral details such as data source, units, freshness, or exactly how 'term-structure state' is represented.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded with the core purpose. The bullet list is scannable and useful. Minor redundancy exists because the opening sentence already mentions level, change, and term-structure state, and the 'Returns' section repeats a similar summary, but it does not become verbose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple, parameterless, read-only snapshot tool, the description covers purpose, usage context, and return content. Since there is no output schema, the return description could be more specific (e.g., units of change, what 'context' includes), but overall it gives enough for an agent to decide and invoke correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has zero parameters and 100% schema coverage, so the description has no parameter semantics to explain. The baseline for a parameterless tool is 4, and the description adequately focuses on the tool's output rather than inputs.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Get the current VIX snapshot' with an explicit resource (VIX) and the specific data components: level, change, and term-structure state. The listed use cases ('overall market fear level', 'index vol elevated or calm', 'vol regime context') help distinguish it from sibling tools like get_term_structure or get_iv_rank.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear 'Use this tool when' guidance with concrete user intents, which is helpful for selection. However, it does not explicitly mention when not to use it or name alternative tools, so it stops short of full exclusionary guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.